CHAPTER XXVII--THE GIRLS' DISCOVERY

  "Why don't they come back?"

  "What keeps them so long?"

  "I declare this waiting is worse than----"

  "Doing nothing," Cora finished for Bess. "Probably the boys can't findthe kind of chocolates you ordered, pretty little plump maid, andthey're afraid to come back without them."

  "Silly," protested Bess.

  "But they are a long time," said Hazel, she and Belle having uttered thetwo rather impatient sentences at the opening of this chapter.

  The girls were in the bungalow, eating, not exactly bread and honey, butice cream and cake, which Mrs. Floyd had made. And they were talking ofthe absence of Jack and his chums, who had gone to town to telephone toMr. Haight.

  It was now lunch time and the girls, after waiting in vain for the boys,had eaten, and were enjoying their dessert. Or rather, they were tryingto enjoy it under the rather unappetizing influence of impatient worry.

  "If they don't come back pretty soon I'm going down there myself and seeif we can discover anything," Cora declared.

  "Down where?" asked Belle.

  "In the passage, of course. I want to see if we can find where thatqueer noise came from."

  "And who upset the furniture," added Bess.

  "Well, we're on the track of it," said Hazel. "We are pretty certain,now, that whoever did it came up through that sliding door, and wentdown the same way. That accounts for our never seeing any one enter orleave the bungalow after the manifestations, and that's why, after theboys ran over so promptly the time we saw the dancing light, theycouldn't find any one. Whoever it was just slipped down through thesecret passage, pulled the section of flooring back into place, andthere was no trace."

  "But where did they go after they got down in the passage?" asked Belle."They couldn't stay there all the while, and there's no sign of any onethere now, unless they're invisible. They couldn't get past the blockingcement wall."

  "There's something beyond that wall, and we're going to find it!"declared Cora.

  "Perhaps when the boys come back they won't have permission to tear itdown," suggested Bess.

  "Then we'll begin our investigations from the other end," Cora said.

  "What other end?" Hazel questioned.

  "The cave! I think this passage connects with the cave. That wouldexplain a hiding place for whoever has been playing these tricks on us,and making that strange noise."

  "You mean the cave you accidentally discovered yesterday?" asked Belle.

  "Yes," Cora answered. "I'm sure that has something to do with themystery. So if Mr. Haight won't let us open the wall, we may be able tosee what is on the other side by going to the cave, and finding thepassage that connects with the one which comes out into our bungalow."

  "In that event the stone wall must be movable," suggested Hazel.

  Cora jumped up so suddenly that she disturbed Bess who was leaningagainst her.

  "That's it! That's it!" Cora cried. "I wonder we didn't think of itbefore. That surely is it!"

  "What is?" eagerly demanded Belle. "You are talking in riddles."

  "This whole affair is a riddle, girls!" exclaimed Cora. "But what Hazelsaid gave me an idea. That cement wall seems solid, but it can't be. Ifit were no one could pass. So it must be made to look solid to deceivethose not in the secret. Probably it is a balanced stone like the onesyou read of in stories of the cave dwellers. Some of them closed theentrances to their caves by heavy rocks, set on pivots, turning when youpressed on a certain mechanism. There are counterweights, just as in awindow, which makes the heaviest rock move easily. I'm sure that's whatis in the passage--a balanced rock doorway. And there won't be any needof tearing the wall down at all!"

  "It sounds like a detective story," commented Bess.

  "It may turn out to be one before we're through," Cora said.

  "Oh, dear! Why don't those boys hurry back?" cried Belle for perhaps thetenth time. "Let's go out and look down the road to see if they arecoming."

  The girls went out, too anxious and too eager to sit still, but they hadno sight of Jack and his chums.

  "I'm not going to wait any longer!" exclaimed Cora at length. "If I'mright, there will be no need of tearing down the wall. That is, if I canfind the mechanism that turns the rocky door. And if I'm wrong, therewon't be any harm in doing it."

  "Doing what?" asked Bess.

  "Going down into the passage to see what we can discover. Will youcome?"

  "I will!" exclaimed Hazel.

  "Then we will, too, Belle," said Bess, quickly. "They shan't call uscowards, even if we are twins."

  "Come on," cried Cora gaily. "We must do something or fly to pieces withnerves. Anything is better than sitting still, waiting."

  Back to the bungalow the girls hastened. The hole in the floor was stillopen, the sliding door having been braced back so it could not be closedby any accident.

  "We don't want to go down there and not be able to get up again," Coraremarked.

  "Shall we tell Mrs. Floyd we're going to see what we can find?"suggested Belle.

  "No," decided Cora, after a moment's thought. "She might not want us tountil we have Mr. Haight's permission. We'll just do this on our ownresponsibility. We won't damage the wall any."

  Down the cement steps went the four girls, into the dark passage. Theboys had left behind their flashlights and these were carried by Coraand Hazel. The small, but powerful lamps gave a good light.

  "Ugh! It's rather creepy in here," complained Belle, looking back overher shoulder.

  "Don't be silly!" said Cora, sharply. "Just think of it! We may solvethe mystery all by ourselves."

  "Let us hope so," murmured Bess.

  They came to the cement wall that barred further progress along thepassage.

  "First to see if it's solid rock," Cora suggested.

  "How?" asked Belle.

  "By tapping. I brought along a hammer." With this implement Cora gaveseveral blows against the obstruction. An unmistakable hollow soundresulted.

  "I believe it's only a wooden door, covered over with cement stucco,"Cora said. "Now to find the secret catch."

  With their flash lamps the girls went over every inch of the surface ofthe door. At first it all looked alike, dull, gray, smooth cement. ThenCora's light lingered a moment on a certain place.

  "Girls, watch!" she said suddenly.

  With her thumb she pressed on the spot where it seemed the cement wasworn smoother than elsewhere. And then, to the surprise of even Coraherself, the cement door swung slowly back, revealing a dark passagebeyond.

  "We've discovered it!" cried Cora. "No need to tear the door down. Justas I suspected, it's on hinges. Come on, girls!"

  Hardly realizing what they were doing, the others followed, theirtorches illuminating the plank sides of the underground tunnel.

  "Are you sure this is all right, Cora?" asked Belle, as she steppedbeyond the open door.

  "I'm not sure anything is right about all this mystery," was the answer,"but this is a chance we mustn't miss. Come on."

  "But where are we going?" Belle queried.

  "I can't tell, but I think to the cave," Cora answered. "Don't beafraid. There's no danger."

  Hardly had she spoken than a noise sounded behind them.

  "Oh! what's that?" cried Belle, rushing forward.

  "It sounded like a door closing," said Hazel.

  She flashed her light back on the way they had come, and as she did soshe cried:

  "It was the door. It has swung shut, girls! We're trapped!"